1. Fields of the Invention
The present invention relates to a light emitting diode (LED), and particularly to a structure of LED and a flip-chip LED package.
2. Descriptions of Related Art
An LED constructed by an III-V semiconductor material is a wide bandgap light emitting device. The wavelength of the light emitted from the wide bandgap light emitting device ranges from infrared to ultraviolet, covering the entire wavelength of the visible light. Along with the fast development of the high brightness of the gallium nitride (GaN) LEDs, the applications of full-color LED displays, white light LED and the LED for traffic signals are put into practice. Therefore, the various applications of LEDs also become more popular.
A fundamental structure of the LED includes an n-type doped semiconductor layer, a p-type doped semiconductor layer, and a light emitting layer disposed in-between. The light emitting efficiency of the LED depends on the internal quantum efficiency of the light emitting layer and the light extraction efficiency of the LED. Thus, the light emitting efficiency of the LED can be improved by increasing the internal quantum efficiency and the light extraction efficiency. A method of increasing the internal quantum efficiency includes improving the epitaxy quality as well as the structural design. The method of increasing the light extraction efficiency includes reducing the energy loss caused by reflection of the light emitted from the light emitting layer inside the LED.
A conventional LED includes a positive electrode and a negative electrode which are set on the same surface. Yet both the positive and negative electrodes will screen out the light emitted from the light emitting layer. Thus, a structure of flip-chip LED package is provided. The positive and negative electrodes are facing an opaque substrate and a reflection layer is used for making the light emit toward the opposite side of the electrodes. Moreover, if a proper surface-mount substrate such as a silicon one is applied to the structure of flip-chip LED package, the better heat dissipation is attained especially under an operating environment with high current. Thus, the light extraction efficiency of the LED is increased and the internal quantum efficiency of the light emitting layer will not be affected by overheating.
However, the above structure of flip-chip LED package still have the problem of the nonuniform distribution of current in the n-type or the p-type doped layer, which leads to the deterioration of the electrical properties and the reduction of the light emitting efficiency of the LED.
Thus, the present invention provides a light emitting diode, which solves the problems of the nonuniform distribution of current and the LED overheating. Thereby, the light emitting efficiency of the LED is improved.